INLS 560 – P ROGRAMMING FOR I NFORMATION P ROFESSIONALS Instructor: Jason Carter

A P ROGRAM Set of instructions that a computer follows to perform a task or solve a problem

P IAZZA Signup Link: piazza.com/unc/fall2014/560 Class page: piazza.com/unc/fall2014/560/home

W HAT IS A P ROGRAM ? Set of instructions that a computer follows to perform a task or solve a problem

P EANUT B UTTER & J ELLY S ANDWICH

W HAT D ID WE L EARN F ROM T HIS E XERCISE ? Computers are dumb! Computers only do what you tell them to do. Computers do what you tell them to do really fast, so they appear smart (but they are not). Computers don’t remember anything unless you tell them how to remember. Computers take your instructions literally. If you tell them to do something dumb, they do it. Computers only do what they are told and in exactly the order you tell them.

W HAT L ANGUAGE D O C OMPUTERS U NDERSTAND ? A computer understands 1’s and 0’s Sequences of 1’s and 0’s Operation Examples: reading data, adding, subtracting, multiplying, and dividing numbers CPU (Central Processing Unit) Reads instructions from memory Decodes fetched instruction to determine which operation to perform Perform the operation

M ACHINE L ANGUAGE Reasons for not using machine language Virtually unreadable.. Hard maintain and debug. No mathematical functions available (we need to create our own code for these routines every time we write a new program). Memory locations are manipulated directly, requiring the programmer to keep track of every memory location on the computer! (How much memory does your computer have?)

O VERCOME D IFFICULTY OF U SING M ACHINE L ANGUAGE Want to use a English like language Computers only understand machine language( 1’s and 0’s) English Like Language Converter Machine Language

H IGH L EVEL L ANGUAGES Compiled Java, C#, C++ Interpreted Python, PHP

C OMPILED L ANGUAGES A compiler reads the program and translates it completely before the program starts running. Java, C#, C++ Compiler Machine Language

I NTERPRETED L ANGUAGES Interpreter reads code and performs operations one line at a time. Python, PHP Interpeter Machine Language

W HICH H IGH L EVEL L ANGUAGE S HOULD WE U SE ? Compiled Java, C#, C++ Interpreted Python, PHP We will use Python.

W HY P YTHON ? C++ #include void main() { cout << "Hello, world." << endl; } Python print "Hello, World!" Simpler than other languages

W HY P YTHON ? Modern language. Good Error Detection. Rich Library Embodying Many Good Programming Principles

R EVIEW Computers understand machine language. We will be using Python. Python is an interpreted language. How do we use the Python interpreter? Interactive mode: enter statements on keyboard Script mode: save statements in Python script

S CRIPT M ODE Save a set of Python statements in a file The filename should have the.py extension

I NTEGRATED D EVELOPMENT E NVIRONMENT (IDE) A program that provides tools to write, execute, and test a program Pycharm Community Edition Runs in interactive mode Has built-in text editor with features designed to help write Python programs

P ROGRAMS